Use of creatine or creatine analogs for the treatment of diseases of the nervous system

ABSTRACT

The present invention relates to the use of creatine compounds including creatine, creatine phosphate or analogs of creatine, such as cyclocreatine, for treating diseases of the nervous system. Creatine compounds can be used as therapeutically effective agents against a variety of diseases of the nervous system such as diabetic and toxic neuropathies, peripheral nervous system diseases, Alzheimer&#39;s disease, Parkinson&#39;s disease, stroke, Huntington&#39;s disease, amyotropic lateral sclerosis, motor neuron disease, traumatic nerve injury, multiple sclerosis, dysmyelination and demyelination disorders, and mitochondrial diseases. The creatine compounds which can be used in the present method include (1) creatine, creatine phosphate and analogs of these compounds which can act as substrates or substrate analogs for creatine kinase; (2) bisubstrate inhibitors of creatine kinase comprising covalently linked structural analogs of adenosine triphosphate (ATP) and creatine; (3) creatine analogs which can act as reversible or irreversible inhibitors of creatine kinase; and (4) N-phosphorocreatine analogs bearing non-transferable moieties which mimic the N-phosphoryl group.

RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 08/853,174, filed on May 7, 1997, which which is a nationalstage of PCT Application PCT/U.S.95/14567, which was filed on Nov. 7,1995, which claims priority to U.S. patent application Ser. No.08/336,388, filed on Nov. 8,1994. The entire contents of each of theaforementioned patent applications are hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] Creatine is a compound which is naturally occurring and is foundin mammalian brain and other excitable tissues, such as skeletal muscle,retina and heart. Its phosphorylated form, creatine phosphate, also isfound in the same organs and is the product of the creatine kinasereaction utilizing creatine as a substrate. Creatine and creatinephosphate can be synthesized relatively easily and are believed to benon-toxic to mammals. Kaddurah-Daouk et al. (WO 92/08456, published May29, 1992 and WO 90/09192, published Aug. 23, 1990; U.S. Pat. No.5,321,030; and U.S. Pat. No. 5,324,731) describe methods of inhibitingthe growth, transformation and/or metastasis of mammalian cells usingrelated compounds. Examples of compounds described by Kaddurah-Daouk etal. include cyclocreatine, b-guandidino propionic acid,homocyclocreatine, 1-carboxymethyl-2-iminohexahydropyrimidine, guanidinoacetate and carbocreatine. These same inventors have also demonstratedthe efficacy of such compounds for combating viral infections (U.S. Pat.No. 5,321,030). Elebaly in U.S. Pat. No. 5,091,404 discloses the use ofcyclocreatine for restoring functionality in muscle tissue. Cohn in PCTpublication No. WO94/16687 described a method for inhibiting the growthof several tumors using creatine and related compounds.

[0003] The nervous system is an unresting assembly of cells thatcontinually receives information, analyzes and perceives it and makesdecisions. The principle cells of the nervous system are neurons andneuroglial cells. Neurons are the basic communicating units of thenervous system and possess dendrites, axons and synapses required forthis role. Neuroglial cells consist of astrocytes, oligodendrocytes,ependymal cells, and microglial cells. Collectively, they are involvedin the shelter and maintenance of neurons. The functions of astrocytesare incompletely understood but probably include the provision ofbiochemical and physical support and aid in insulation of the receptivesurfaces of neurons. In addition to their activities in normal brain,they also react to CNS injury by glial scar formation. The principlefunction of the oligodendrocytes is the production and maintenance ofCNS myelin. They contribute segments of myelin sheath to multiple axons.

[0004] The ependyma cells react to injury mainly by cell loss.Microglial cells become activated and assume the shape of a macrophagein response to injury or destruction of the brain. These cells can alsoproliferate and adopt a rod-like form which could surround a tiny focusof necrosis or a dead neuron forming a glial nodule. Microglialdegradation of dead neurons is called neuronophagia.

[0005] The creatine kinase/creatine phosphate energy system is only onecomponent of an elaborate energy-generating system found in nervoussystem cells such as, for example, neurons, oligodendrocytes andastrocytes. The components of the creatine energy system include theenzyme creatine kinase, the substrates creatine and creatine phosphate,and the transporter of creatine. The reaction catalyzed by creatinekinase is: MgADP±PCr⁼+H^(+MgATP) ⁼+Cr. Some of the functions associatedwith this system include efficient regeneration of energy in cells withfluctuating and high energy demands, energy transport to different partsof the cell, phosphoryl transfer activity, ion transport regulation, andinvolvement in signal transduction pathways.

[0006] The creatine kinase/phosphocreatine system has been shown to beactive in neurons, astrocytes, oligodendrocytes and Schwann cells. Manoset al., J. Neurochem. 56:2101-2107 (1991); Molloy et al., J. Neurochem.59:1925-1932. The activity of the enzyme has been shown to beup-regulated during regeneration and down-regulated in degenerativestates (see, e.g., Annals Neurology 35(3):331-340 (1994); DeLeon et al.,J.Neuruosci. Res. 29:437448 (1991); Orlovskaia et al. Vestnik RossiiskoiAkademii Meditsinskikh Nauk. 8:34-39 (1992). Burbaeva et al., ShumalNeuropathologll Psikhiatrii Imeni S-S-Korsakova 90(7):85-87 (1990);Mitochondrial creatine kinase was recently found to be the majorconstituent of pathological inclusions seen in mitochondrial myopathies.Stadhouders et al., PNAS, 91, pp 5080-5093 (1994).

[0007] It is an object of the present invention to provide methods fortreatment of diseases that affect cells of the nervous system thatutilize the creatine kinase/phosphocreatine system using compounds whichmodulate the system.

SUMMARY OF THE INVENTION

[0008] The present invention pertains to methods of treating diseases ofthe nervous systems in an individual afflicted with such a disease byadministering to the afflicted individual an amount of a compound orcompounds which modulate one or more of the structural or functionalcomponents of the creatine kinase/phosphocreatine system sufficient toprevent, reduce or ameliorate the symptoms of the disease. Compoundswhich are effective for this purpose include creatine, creatinephosphate, and analogs of creatine or creatine phosphate.

[0009] The present invention also provides compositions containingcreatine compounds in combination with a pharmaceutically acceptablecarrier, and effective amounts of other agents which act on the nervoussystem, to prophylactically and/or therapeutically treat a subject witha disease of the nervous system. The present invention further pertainsto methods of use of creatine compounds in combination with other agentswhich act on the nervous system for treating diseases of the nervoussystem.

[0010] Packaged drugs for treating subjects having a disease of thenervous system or one who is predisposed to such diseases also are thesubject of the present invention. The packaged drugs include a containerholding the creatine compound, in combination with a pharmaceuticallyacceptable carrier, along with instructions for administering the samefor the purpose of preventing, ameliorating, arresting or eliminating adisease of the nervous system.

[0011] Some of the diseases susceptible to treatment with creatinecompounds according to the present invention include, but are notlimited to Alzheimer disease, Parkinson's disease, Huntington's disease,motor neuron disease, diabetic and toxic neuropathies, traumatic nerveinjury, multiple sclerosis, acute disseminated encephalomyelitis, acutenecrotizing hemorrhagic leukoencephalitis, diseases of dysmyelination,mitochondrial diseases, fungal and bacterial infections, migrainousdisorders, stroke, aging, dementia, and mental disorders such asdepression and schizophrenia.

BRIEF DESCRIPTION OF THE FIGURES

[0012]FIG. 1 is a graph illustrating the effect of creatine compounds onlesion volumes in mice using the malonate model.

[0013]FIG. 2 is a graph illustrating the effect of creatine compounds onlevels of dopamine, HVA, and DOPAC in mice using the MPTP animal model.

DETAILED DESCRIPTION

[0014] The methods of the present invention generally compriseadministering to an individual afflicted with a disease of the nervoussystem an amount of a compound or compounds which modulate one or moreof the structural or functional components of the creatinekinase/phosphocreatine system sufficient to prevent, reduce orameliorate symptoms of the disease. Components of the system which canbe modulated include the enzyme creatine kinase, the substrates creatineand creatine phosphate, and the transporter of creatine. As used herein,the term “modulate” means to change, affect or interfere with the normalfunctioning of the component in the creatine kinase/phosphocreatineenzyme system.

[0015] Compounds which are particularly effective for this purposeinclude creatine, creatine phosphate, and analogs thereof which aredescribed in detail below. The term “creatine compounds” will be usedherein to include creatine, creatine phosphate, and compounds which arestructurally similar to creatine or creatine phosphate, and analogs ofcreatine and creatine phosphate. The term “creatine compounds” alsoincludes compounds which “mimic” the activity of creatine, creatinephosphate or creatine analogs, i.e., compounds which inhibit or modulatethe creatine kinase system. The term “mimics” is intended to includecompounds which may not be structurally similar to creatine but mimicthe therapeutic activity of creatine, creatine phosphate or structurallysimilar compounds. The term “inhibitors of creatine kinase system” arecompounds which inhibit the activity of the creatine kinase enzyme,molecules that inhibit the creatine transporter or molecules thatinhibit the binding of the enzyme to other structural proteins orenzymes or lipids. The term “modulators of the creatine kinase system”are compounds which modulate the activity of the enzyme, or the activityof the transporter of creatine or the ability of other proteins orenzymes or lipids to interact with the system. The term “creatineanalog” is intended to include compounds which are structurally similarto creatine or creatine phosphate, compounds which are art-recognized asbeing analogs of creatine or creatine phosphate, and/or compounds whichshare the same or similar function as creatine or creatine phosphate.

[0016] The language “treating diseases of the nervous system” isintended to include prevention of the disease, amelioration and/orarrest of a preexisting disease, and the elimination of a preexistingdisease. The creatine analogs described herein have both curative andprophylactic effects on disease development and progression.

[0017] The language “therapeutically effective amount” is intended toinclude the amount of the creatine compound sufficient to prevent onsetof diseases of the nervous system or significantly reduce progression ofsuch diseases in the subject being treated. A therapeutically effectiveamount can be determined on an individual basis and will be based, atleast in part, on consideration of the severity of the symptoms to betreated and the activity of the specific analog selected if an analog isbeing used. Further, the effective amounts of the creatine compound mayvary according to the age, sex and weight of the subject being treated.Thus, a therapeutically effective amount of the creatine compound can bedetermined by one of ordinary skill in the art employing such factors asdescribed above using no more than routine experimentation in clinicalmanagement.

[0018] The language “pharmaceutically acceptable carrier” is intended toinclude substances capable of being coadministered with the creatinecompound and which allows the active ingredient to perform its intendedfunction of preventing, ameliorating, arresting, or eliminating adisease(s) of the nervous system. Examples of such carriers includesolvents, dispersion media, adjuvants, delay agents and the like. Theuse of such media and agents for pharmaceutically active substances iswell known in the art. Any conventional media and agent compatible withthe creatine compound may be used within this invention.

[0019] The term “pharmaceutically acceptable salt” is intended toinclude art-recognized pharmaceutically acceptable salts. Typicallythese salts are capable of being hydrolyzed under physiologicalconditions. Examples of such salts include sodium, potassium andhemisulfate. The term further is intended to include lower hydrocarbongroups capable of being hydrolyzed under physiological conditions, i.e.groups which esterify the carboxyl moiety, e.g. methyl, ethyl andpropyl.

[0020] The term “subject” is intended to include living organismssusceptible to having diseases of the nervous system, e.g. mammals.Examples of subjects include humans, dogs, cats, horses, cows, goats,rats and mice. The term “subject” further is intended to includetransgenic species.

[0021] The language “diseases of the nervous system” is intended toinclude diseases of the nervous system whose onset, amelioration,arrest, or elimination is effectuated by the creatine compoundsdescribed herein. Examples of types of diseases of the nervous systeminclude demyelinating, dysmyelinating and degenerative diseases.Examples of locations on or within the subject where the diseases mayoriginate and/or reside include both central and peripheral loci. As theterm “disease” is used herein, it is understood to exclude, and onlyencompass maladies distinct from, neoplastic pathologies and tumors ofthe nervous system, inschemic injury and viral infections of the nervoussystem. Examples of types of diseases suitable for treatment with themethods and compounds of the instant invention are discussed in detailbelow.

[0022] Diseases of the Nervous System

[0023] Diseases of the nervous system fall into two general categories:(a) pathologic processes such as infections, trauma and neoplasma foundin both the nervous system and other organs; and, (b) diseases unique tothe nervous system which include diseases of myelin and systemicdegeneration of neurons.

[0024] Of particular concern to neurologists and other nervous systempractitioners are diseases of: (a) demyelination which can develop dueto infection, autoimmune antibodies, and macrophage destruction; and,(b) dysmyelination which result from structural defects in myelin.

[0025] Diseases of neurons can be the result of: (a) aberrant migrationof neurons during embryogenesis and early stage formation; or (b)degenerative diseases resulting from a decrease in neuronal survival,such as occurs in, for example, Alzheimer's disease, Parkinson'sdisease, Huntington's disease, motor neuron disease, ischemia-relateddisease and stroke, and diabetic neuropathy.

[0026] Demvelinating Diseases:

[0027] Primary demyelination is a loss of myelin sheaths with relativepreservation of the demyelinated axons. It results either from damage tothe oligodendroglia which make the myelin or from a direct, usuallyimmunologic or toxic attack on the myelin itself. Secondarydemyelination, in contrast, occurs following axonal degeneration. Thedemyelinating diseases are a group of CNS conditions characterized byextensive primary demyelination. They include multiple sclerosis and itsvariants and perivenous encephalitis. There are several other diseasesin which the principal pathologic change is primary demyelination, butwhich are usually conveniently classified in other categories such asinborn errors of metabolism, the leukodystrophies, viral disease(progressive multifocal leukoencephalopathy PM), as well as severalother rare disorders of unclear etiology.

[0028] Multiple Sclerosis (MS)

[0029] Multiple sclerosis is a disease of the central nervous system(CNS) that has a peak onset of 30-40 years. It affects all parts of theCNS and causes disability related to visual, sensory, motor, andcerebellar systems. The disease manifestations can be mild andintermittent or progressive and devastating. The pathogenesis is due toan autoimmune attack on CNS myelin. The treatments available aresymptomatic treating spasticity, fatigue, bladder dysfunction, andspasms. Other treatments are directed towards stopping the immunologicattack on myelin. These consist of corticosteroids such as prednisoneand methylprednisolone, general immunosuppressants such ascyclophosphamide and azathioprine, and immunomodulating agents such asbeta-interferon. No treatments are available to preserve myelin or makeit resistant to attacks.

[0030] Acute Disseminated Encephalomyelitis

[0031] Acute Disseminated Encephalomyelitis usually occurs following aviral infection and is thought to be due to an autoimmune reactionagainst CNS myelin, resulting in paralysis, lethargy, and coma. Itdiffers from MS by being a monophasic disease whereas MS ischaracterized by recurrence and chronicity. Treatment consists ofadministration of steroids.

[0032] Acute Necrotizing Hemorrhagic Leukoencephalitis

[0033] This is a rare disease that is generally fatal. It is alsothought to be mediated by autoimmune attack on CNS myelin that istriggered by a viral infection. Neurologic symptoms develop abruptlywith headache, paralysis and coma. Death usually follows within severaldays. Treatment is supportive.

[0034] Leukodystrophies:

[0035] These are diseases of the white matter resulting from an error inthe myelin metabolism that leads to impaired myelin formation. They arethought of as dysmyelinating diseases, and can become manifest at anearly age.

[0036] Metachromatic Leukodystrophy: an autosomal recessive (inherited)disorder due to deficiency of the enzyme arylsulfatase A leading toaccumulation of lipids. There is demyelination in the CNS and peripheralnervous system leading to progressive weakness and spasticity.

[0037] Krabbe's disease: Also inherited as autosomal recessive and dueto deficiency of another enzyme: galctocerebroside beta-galactosidase.

[0038] Adrenoleukodystrophy and adrenomyeloneuropathy: affect theadrenal glad in addition to the nervous system.

[0039] No treatment is available to any of the leukodystrophies exceptfor supportive treatment.

[0040] Degenerative Diseases:

[0041] There is no good etiology or pathophysiology known for thesediseases, and no compelling reason to assume that they all have asimilar etiology. Diseases under this category have generalsimilarities. They are diseases of neurons that tend to result inselective impairment, affecting one or more functional systems ofneurons while leaving others intact.

[0042] Parkinson's Disease:

[0043] Parkinson's disease is due to loss of dopaminergic neurones inthe substantia nigra of the brain. It is manifested by slowed voluntarymovements, rigidity, expressionless face and stooped posture. Severaldrugs are available to increase dopaminergic function such as levodopa,carbidopa, bromocriptine, pergolide, or decrease cholinergic functionsuch as benztropine, and amantadine. Selegiline is a new treatmentdesigned to protect the remaining dopaminergic neurons.

[0044] Spinocerebellar Degenerations

[0045] This is a group of degenerative diseases that affects in varyingdegrees the basal ganglia, brain stem, cerebellum, spinal cord, andperipheral nerves. Patients present symptoms of Parkinsonism, ataxia,spasticity, and motor and sensory deficits reflecting damage todifferent anatomic areas and/or neuronal systems in the CNS.

[0046] Degenerative Disease Affecting Motor Neurons

[0047] Included in this category are diseases such as amyotrophiclateral sclerosis (ALS), and spinal muscular atrophy. They arecharacterized by degeneration of motor neurones in the CNS leading toprogressive weakness, muscle atrophy, and death caused by respiratoryfailure. Treatments are only symptomatic, there are no availabletreatments to slow down or stop the disease.

[0048] Alzheimer Disease (AD):

[0049] This disease is characterized clinically by slow erosion ofmental function, culminating in profound dementia. The diagnosticpathologic hallmark of AD is the presence of large numbers of senileplagues and neurofibrillary tangles in the brain especially in neocortexand hippocampus. Loss of specific neuron populations in these brainregions and in several subcortical nuclei correlates with depletion incertain neurotransmitters including acetylcholine. The etiology of AD isstill unknown. To date a lot of research has focused on the compositionand genesis of the B/A4 amyloid component of senile plagues. Alzheimer'sdisease is characterized clinically by the slow erosion of intellectualfunction with the development of profound dementia. There are notreatments that slow the progression.

[0050] Huntington Disease (HD):

[0051] HD is an autosomal dominant disorder of midlife onset,characterized clinically by movement disorder, personality changes, anddementia often leading to death in 15-20 years. The neuropathologicchanges in the brain are centered in the basal ganglia. Loss of a classof projection neurons, called “spiny cells” because of their prominentdendritic spinous processes, is typical. This class of cells containsgamma-aminobutyric acid (GABA), substance P, and opioid peptides.Linkage studies have localized the gene for HD to the most distal bandof the short arm of chromosome 4. No treatments are available that havebeen shown to retard progression of the disease. Experimental studiesshowing a similarity between neurons that are susceptible to N-methyld-aspartate (NMDA) agonists and those that disappear in HD has led toencouraging speculation that NMDA antagonists might prove beneficial.Some recent studies suggest that a defect in brain energy metabolismmight occur in HD and enhance neuronal vulnerability to excitotoxicstress.

[0052] Mitochondrial Encephalomyopathies:

[0053] Mitochondrial encephalomyopathies are a heterogenous group ofdisorders affecting mitochondrial metabolism. These deficits couldinvolve substrate transport, substrate utilization, defects of the KrebsCycle, defects of the respiratory chain, and defects ofoxidation/phosphorylation coupling. Pure myopathies vary considerablywith respect to age at onset, course (rapidly progressive, static, oreven reversible), and distribution of weakness (generalized withrespiratory failure, proximal more than distal facioscapulohumeral,orbicularis and extraocular muscles with ptosis and progressive externalophthalmoplegia). Patients with mitochondrial myopathies complain ofexercise intolerance and premature fatigue.

[0054] Peripheral Nervous System Disorders

[0055] The peripheral nervous system (PNS) consists of the motor andsensory components of the cranial and spinal nerves, the autonomicnervous system with its sympathetic and parasympathetic divisions, andthe peripheral ganglia. It is the conduit for sensory information to theCNS and effector signals to the peripheral organs such as muscle.Contrary to the brain, which has no ability to regenerate, thepathologic reactions of the PNS include both degeneration andregeneration. There are three basic pathological processes: Walleriandegeneration, axonal degeneration and segmental demyelination that couldtake place.

[0056] Some of the neuropathic syndromes include:

[0057] Acute ascending motor paralysis with variable sensorydisturbance; examples being acute demyelinating neuropathics, infectiousmononucleosis with polyneuritis, hepatitis and polyneuritis, toxicpolyneuropathies.

[0058] Subacute sensorimotor polyneuropathy; examples of acquired axonalneurophathics include paraproteinemias, uremia diabetes, arnyloidosis,connective tissue diseases and leprosy. Examples of inherited diseasesinclude mostly chronic demyelination with hypertrophic changes, such asperoneal muscular atrophy, hypertrophic polyneuropathy and Refsum'sdiseases.

[0059] Chronic relapsing polyneuropathy; such as idiopathic polyneuritisporphyria, Beriberi and intoxications.

[0060] Mono or multiple neuropathy; such as pressure palsies, traumaticpalsies, serum neuritis, zoster and leprosy.

[0061] Creatine Compounds Useful For Treating Nervous System Diseases

[0062] Creatine compounds useful in the present invention includecompounds which modulate one or more of the structural or functionalcomponents of the creatine kinase/phosphocreatine system. Compoundswhich are effective for this purpose include creatine, creatinephosphate and analogs thereof, compounds which mimic their activity, andsalts of these compounds as defined above. Exemplary creatine compoundsare described below.

[0063] Creatine (also known as N-(aminoininomethyl)-N-methylglycine;methylglycosamine or N-methyl-guanido acetic acid) is a well-knownsubstance. (See, The Merck Index, Eleventh Edition, No. 2570 (1989).

[0064] Creatine is phosphorylated chemically or enzymatically bycreatine kinase to generate creatine phosphate, which also is well-known(see The Merck Index, No. 7315). Both creatine and creatine phosphate(phosphocreatine) can be extracted from animal tissue or synthesizedchemically. Both are commercially available.

[0065] Cyclocreatine is an essentially planar cyclic analog of creatine.Although cyclocreatine is structurally similar to creatine, the twocompounds are distinguishable both kinetically and thermodynamically.Cyclocreatine is phosphorylated efficiently by creatine kinase in theforward reaction both in vitro and in vivo. Rowley, G. L., J. Am. Chem.Soc. 93: 5542-5551 (1971); McLaughlin, A. C. et. al., J. Biol. Chem.247, 4382-4388 (1972).

[0066] The phosphorylated compound phosphocyclocreatine is structurallysimilar to phosphocreatine; however, the phosphorous-nitrogen (P—N) bondof cyclocreatine phosphate is more stable than that of phosphocreatine.LoPresti, P. and M. Cohn, Biochem. Biophys. Acta 998: 317-320 (1989);Annesley, T. M. and J. B. Walker, J. Biol. Chem. 253; 8120-8125, (1978);Annesley, T. M. and J. B. Walker, Biochem. Biophys. Res. Commun. 74:185-190 (1977).

[0067] Creatine analogs and other agents which act to interfere with theactivity of creatine biosynthetic enzymes or with the creatinetransporter are useful in the present method of treating nervous systemdiseases. In the nervous system, there are many possible intracellular,as well as extracellular, sites for the action of compounds thatinhibit, increase, or otherwise modify, energy generation through braincreatine kinase and/or other enzymes which are associated with it. Thusthe effects of such compounds can be direct or indirect, operating bymechanisms including, but not limited to, influencing the uptake orbiosynthesis of creatine, the function of the creatine phosphateshuttle, inhibiting the enzyme activity, or the activity of associatedenzymes, or altering the levels of substrates or products of a reactionto alter the velocity of the reaction.

[0068] Substances known or believed to modify energy production throughthe creatine kinase/phosphocreatine system which can be used in thepresent method are described below. Exemplary compounds are shown inTables 1 and 2. TABLE 1 CREATINE ANALOGS

[0069] TABLE 2 CREATINE PHOSPHATE ANALOGS

[0070] It will be possible to modify the substances described below toproduce analogs which have enhanced characteristics, such as greaterspecificity for the enzyme, enhanced stability, enhanced uptake intocells, or better binding activity.

[0071] Compounds which modify the structure or function of the creatinekinase/creatine phosphate system directly or indirectly are useful inpreventing and/or treating diseases of the nervous system characterizedby up regulation or down regulation of the enzyme system.

[0072] In diseases where the creatine kinase/creatine phosphate systemis down regulated, for example, uncontrolled firing of neurons,molecules useful for treating these diseases include those that will upregulate the activity, or could support energy (ATP) production for alonger period of time. Examples include creatine phosphate and relatedmolecules that form stable phosphagens which support ATP production overa long period of time.

[0073] In diseases where the creatine kinase/creatine phosphate systemis up regulated, the molecules that are useful include those that willdown regulate the activity and/or inhibit energy production (ATP).

[0074] Molecules that regulate the transporter of creatine, or theassociation of creatine kinase with other protein or lipid molecules inthe membrane, the substrates concentration creatine and creatinephosphate also are useful in preventing and/or treating diseases of thenervous system.

[0075] Compounds which are useful in the present invention can beinhibitors, substrates or substrate analogs, of creatine kinase, whichwhen present, could modify energy generation or high energy phosphoryltransfer through the creatine kinase/phosphocreatine system. Inaddition, modulators of the enzymes that work in conjunction withcreatine kinase now can be designed and used, individually, incombination or in addition to other drugs, to make control of the effecton brain creatine kinase tighter.

[0076] The pathways of biosynthesis and metabolism of creatine andcreatine phosphate can be targeted in selecting and designing compoundswhich may modify energy production or high energy phosphoryl transferthrough the creatine kinase system. Compounds targeted to specific stepsmay rely on structural analogies with either creatine or its precursors.Novel creatine analogs differing from creatine by substitution, chainextension, and/or cyclization may be designed. The substrates ofmultisubstrate enzymes may be covalently linked, or analogs which mimicportions of the different substrates may be designed. Non-hydrolyzablephosphorylated analogs can also be designed to mimic creatine phosphatewithout sustaining ATP production.

[0077] A number of creatine and creatine phosphate analogs have beenpreviously described in the literature or can be readily synthesized.Examples are these shown in Table 1 and Table 2. Some of them are slowsubstrates for creatine kinase.

[0078] Tables 1 and 2 illustrate the structures of creatine,cyclocreatine (1-carboxymethyl-2-iminoimidazolidine),N-phosphorocreatine (N-phosphoryl creatine), cyclocreatine phosphate(3-phosphoryl-1-carboxymethyl-2-iminoimidazolidine) and other compounds.In addition, 1-carboxymethyl-2-aminoimidazole, 1-carboxymethyl-22-iminomethylimidazolidine, 1-carboxyethyl-2-iminoimidazolidine,N-ethyl-N-amidinoglycine and b-guanidinopropionic acid are believed tobe effective.

[0079] Cyclocreatine (1-carboxymethyl-2-iminoiridazolidine) is anexample of a class of substrate analogs of creatine kinase, which can bephosphorylated by creatine kinase and which are believed to be active.

[0080] A class of creatine kinase targeted compounds are bi-substrateanalogs comprising an adenosine-like moiety linked via a modifiablebridge to a creatine link moiety (i.e., creatine or a creatine analog).Such compounds are expected to bind with greater affinity than the sumof the binding interaction of each individual substrate (e.g., creatineand ATP). The modifiable bridge linking an adenosine-like moiety at the5′-carbon to a creatine like moiety can be a carbonyl group, alkyl (abranched or straight chain hydrocarbon group having one or more carbonatoms), or substituted alkyl group (an alkyl group bearing one or morefunctionalities, including but not limited to unsaturation,heteroatom-substituents, carboxylic and inorganic acid. derivatives, andelectrophilic moieties).

[0081] Another class of potential compounds for treating nervous systemdisorders is designed to inhibit (reversibly or irreversibly) creatinekinase. The analogs of creatine in this class can bind irreversibly tothe active site of the enzyme. Two such affinity reagents that havepreviously been shown to completely and irreversibly inactivate creatinekinase are epoxycreatine Marietta, M. A. and G. L. Kenyon J. Biol Chem.254: 1879-1886 (1979)) and isoepoxycreatine Nguyen, A. C. K., Ph.D.dissertation in Pharmaceutical Chemistry, (University of California, SanFrancisco, 1983), pp. 112-205). There are several approaches toenhancing the specificity and hence, the efficacy of activesite-targeted irreversible inhibitors of creatine kinase, incorporatingan electrophilic moiety. The effective concentration of a compoundrequired for inhibition can be lowered by increasing favorable anddecreasing unfavorable binding contacts in the creatine analog.

[0082] N-phosphorocreatine analogs also can be designed which bearnon-transferable moieties which mimic the N-phosphoryl group. Thesecannot sustain ATP production.

[0083] Some currently preferred creatine compounds of this invention arethose encompassed by the general formula I:

[0084] and pharmaceutically acceptable salts thereof, wherein:

[0085] a) Y is selected from the group consisting of: —CO₂H—NHOH, —NO₂,—SO₃H, —C(═O)NHSO₂J and —P(═O)(OH)(OJ), wherein J is selected from thegroup consisting of hydrogen, C₁-C₆ straight chain alkyl, C₃-C₆ branchedalkyl, C₂-C₆ alkenyl C₃-C₆ branched alkenyl, and aryl;

[0086] b) A is selected from the group consisting of: C, CH, C₁-C₅alkyl,C₂-C₅alkenyl, C₂-C₅alkynyl, and C₁-C₅alkoyl chain, each having 0-2substituents which are selected independently from the group consistingof:

[0087] 1) K, where K is selected from the group consisting of: C₁-C₆straight alkyl C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆branched alkyl, C₃-C₆ branched alkenyl, and C₄-C₆ branched alkoyl, Khaving 0-2 substituents independently selected from the group consistingof: rromo, chloro, epoxy and acetoxy;

[0088] 2) an aryl group selected from the group consisting of: a 1-2ring carbocycle and a 1-2 ring heterocycle, wherein the aryl groupcontains 0-2 substituents independently selected from the groupconsisting of: —CH₂L and —COCH₂L where L is independently selected fromthe group consisting of: bromo, chloro, epoxy and acetoxy; and

[0089] 3) —NH—M, wherein M is selected from the group consisting of:hydrogen, C₁-C₄ alkyl, C₂-C₄ alkenyl, C₁-C₄ alkoyl, C₃-C₄ branchedalkoyl, C₃-C₄ branched alkenyl and C₄ branched alkoyl;

[0090] c) X is selected from the group consisting of NR₁, CHR₁, CR₁, Oand S, wherein R₁ is selected from the group consisting of:

[0091] 1) hydrogen;

[0092] 2) K where K is selected from the group consisting of: C₁-C₆straight alkyl, C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆branched alkyl, C₃-C₆ branched alkenyl, and C₄-C₆ branched alkoyl, Khaving 0-2 substituents independently selected from the group consistingof: bromo, chloro, epoxy and acetoxy;

[0093] 3) an aryl group selected from the group consisting of a 1-2 ringcarbocycle and a 1-2 ring heterocycle, wherein the aryl group contains0-2 substituents independently selected from the group consisting of:—CH₂L and —COCH₂L where L is independently selected from the groupconsisting of: bromo, chloro, epoxy and acetoxy;

[0094] 4) a C₅-C₉ a-amino-w-methyl-w-adenosylcarboxylic acid attachedvia the w-methyl carbon;

[0095] 5) 2 C₅-C₉ a-amino-w-aza-w-methyl-w-adenosylcarboxylic acid.attached via the w-methyl carbon; and

[0096] 6) a C₅-C₉ a-amino-w-thia-w-methyl-w-adenosylcarboxylic acidattached via the w-methyl carbon;

[0097] d) Z₁ and Z₂ are chosen independently from the group consistingof: ═O, —NHR₂, —CH₂R₂, —NR₂OH; wherein Z₁ and Z₂ may not both be ═O andwherein R₂ is selected from the group consisting of:

[0098] 1) hydrogen;

[0099] 2) K, where K is selected from the group consisting of: C₁-C₆straight alkyl; C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆branched alkyl, C₃-C₆ branched alkenyl, and C₄-C₆ branched alkoyl, Khaving 0-2 substituents independently selected from the group consistingof: bromo, chloro, epoxy and acetoxy;

[0100] 3) an aryl group selected from the group consisting of a 1-2 ringcarbocycle and a 1-2 ring heterocycle, wherein the aryl group contains0-2 substituents independently selected from the group consisting of:—CH₂L and —COCH₂L where L is independently selected from the groupconsisting of: bromo, chloro, epoxy and acetoxy;

[0101] 4) 2 C₄-C₈ a-amino-carboxylic acid attached via the w-carbon;

[0102] 5) B, wherein B is selected from the group consisting of:—CO₂H—NHOH, —SO₃H, —NO₂, OP(═O)(OH)(OJ) and —P(═O)(OH)(OJ), wherein J isselected from the group consisting of: hydrogen, C₁-C₆ straight alkyl,C₃-C₆ branched alkyl, C₂-C₆ alkenyl, C₃-C₆ branched alkenyl, and aryl,wherein B is optionally connected to the nitrogen via a linker selectedfrom the group consisting of: C₁-C₂ alkyl, C₂ alkenyl, and C₁-C₂ alkoyl;

[0103] 6) —D—E, wherein D is selected from the group consisting of:C₁-C₃ straight alkyl, C₃ branched alkyl, C₂-C₃ straight alkenyl, C₃branched alkenyl, C₁-C₃ straight alkoyl, aryl and aroyl; and E isselected from the group consisting of: —(PO₃)_(n)NMP, where n is 0-2 andNMP is ribonucleotide monophosphate connected via the 5′-phosphate,3′-phosphate or the aromatic ring of the base; —[P(═O)(OCH₃)(O)]_(m)—Q,where m is 0-3 and Q is a ribonucleoside connected via the ribose or thearomatic ring of the base; —[P(═O)(OH)(CH₂)]_(m)—Q, where m is 0-3 and Qis a ribonucleoside connected via the ribose or the aromatic ring of thebase; and an aryl group containing 0-3 substituents chosen independentlyfrom the group consisting of: Cl, Br, epoxy, acetoxy, —OG, —C(═O)G, and—CO₂G, where G is independently selected from the group consisting of:C₁-C₆ straight alkyl, C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl,C₃-C₆ branched alkyl, C₃-C₆ branched alkenyl, C₄-C₆ branched alkoyl,wherein E may be attached to any point to D, and if D is alkyl oralkenyl, D may be connected at either or both ends by an amide linkage;and

[0104] 7) —E, wherein E is selected from the group consisting of—(PO₃)_(n)NMP, where n is 0-2 and NMP is a ribonucleotide monophosphateconnected via the 5′-phosphate, 3′-phosphate or the aromatic ring of thebase; —[P(═O)(OCH₃)(O)]_(m)—Q, where m is 0-3 and Q is a ribonucleosideconnected via the ribose or the aromatic ring of the base;—[P(═O)(OH)(CH₂)]_(m)—Q, where m is 0-3 and Q is a ribonucleosideconnected via the ribose or the aromatic ring of the base; and an arylgroup containing 0-3 substituents chose independently from the groupconsisting of: Cl, Br, epoxy, acetoxy, —OG, —C(═O)G, and —CO₂G, where Gis independently selected from the group consisting of: C₁-C₆ straightalkyl, C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆ branchedalkyl, C₃-C₆ branched alkenyl, C₄-C₆ branched alkoyl; and if E is aryl,E may be connected by an amide linkage;

[0105] e) if R₁ and at least one R₂ group are present, R₁ may beconnected by a single or double bond to an R₂ group to form a cycle of 5to 7 members;

[0106] f) if two R₂ groups are present, they may be connected by asingle or a double bond to form a cycle of 4 to 7 members; and

[0107] g) if R₁ is present and Z₁ or Z₂ is selected from the groupconsisting of —NHR₂, —CH₂R₂ and —NR₂OH, then R₁ may be connected by asingle or double bond to the carbon or nitrogen of either Z₁ or Z₂ toform a cycle of 4 to 7 members.

[0108] Creatine, creatine phosphate and many creatine analogs, andcompetitive inhibitors are commercially available. Additionally, analogsof creatine may be synthesized using conventional techniques. Forexample, creatine can be used as the starting material for synthesizingat least some of the analogs encompassed by formula I. Appropriatesynthesis reagents, e.g. alkylating, alkenylating or alkynylating agentsmay be used to attach the respective groups to target sites.Alternatively, reagents capable of inserting spacer groups may be usedto alter the creatine structure. Sites other than the target site areprotected using conventional protecting groups while the desired sitesare being targeted by synthetic reagents.

[0109] If the creatine analog contains a ring structure, then the analogmay be synthesized in a manner analogous to that described forcyclocreatine (Wang, T., J. Org. Chem, 39:3591-3594 (1974)). The variousother substituent groups may be introduced before or after the ring isformed.

[0110] Many creatine analogs :have been previously synthesized anddescribed (Rowley et al., J. Am. Chem. Soc. 93:5542-5551 (1971);McLaughlin et al., J. Biol. Chem. 247:4382-4388 (1972); Nguyen, A. C.K., “Synthesis and enzyme studies using creatine analogs”, Thesis, Dept.of Pharmaceutical Chemistry, Univ. Calif., San Francisco (1983); Lowe etal., J. Biol. Chem. 225:3944-3951 (1980); Roberts et al., J. Biol. Chem.260:13502-13508 (1985); Roberts et al., Arch. Biochem. Biophys.220:563-571 (1983), and Griffiths et al., J. Biol. Chem. 251:2049-2054(1976)). The contents of all of the forementioned references areexpressly incorporated by reference. Further to the forementionedreferences, Kaddurah-Daouk et al. (WO92/08456; WO90/09192; U.S. Pat.Nos. 5,324,731; 5,321,030) also provide citations for the synthesis of aplurality of creatine analogs. The contents of all the aforementionedreferences and patents are incorporated herein by reference.

[0111] Creatine compounds which currently are available or have beensynthesized include, for example, creatine, b-guanidinopropionic acid,guanidinoacetic acid, creatine phosphate disodium salt, cyclocreatine,homocyclocreatine, phosphinic creatine, homocreatine, ethylcreatine,cyclocreatine phosphate dilithium salt and guanidinoacetic acidphosphate disodium salt, among others.

[0112] Creatine phosphate compounds also can be synthesized chemicallyor enzymatically. The chemical synthesis is well known. Annesley, T. M.Walker, J. B., Biochem. Biophys. Res. Commun., (1977), 74, 185-190;Cramer, F., Scheiffele, E., Vollmar, A., Chem. Ber., (1 962), 95,1670-1682.

[0113] Salts of the products may be exchanged to other salts usingstandard protocols. The enzymatic synthesis utilizes the creatine kinaseenzyme, which is commercially available, to phosphorylate the creatinecompounds. ATP is required by creatine kinase for phosphorylation, henceit needs to be continuously replenished to drive the reaction forward.It is necessary to couple the creatine kinase reaction to anotherreaction that generates ATP to drive it forward. The purity of theresulting compounds can be confirmed using known analytical techniquesincluding ¹H NMR, ¹³CNMR Spectra, Thin layer chromatography, HPLC andelemental analysis.

[0114] Utility

[0115] In the present invention, the creatine compounds can beadministered to an individual (e.g., a mammal), alone or in combinationwith another compound, for the treatment of diseases of the nervoussystem. As agents for the treatment of diseases of the nervous system,creatine compounds can interfere with creatine kinase/phosphocreatinefunctions, thereby preventing, ameliorating, arresting or eliminatingdirect and/or indirect effects of disease which contribute to symptomssuch as paraplegia or memory impairment. Other compounds which can beadministered together with the creatine compounds includeneurotransmitters, neurotransmitter agonists or antagonists, steroids,corti- costeroids (such as prednisone or methyl prednisone)immunomodulating agents (such as beta-inteferon), immunosuppressiveagents (such as cyclophosphamide or azathioprine), nucleotide analogs,endogenous opioids, or other currently clinically used drugs. Whenco-administered with creatine compounds, these agents can augmentinterference with creatine kinase/phosphocreatine cellular functions,thereby preventing, reducing, or eliminating direct and/or indirecteffects of disease.

[0116] A variety of diseases of the nervous system can be treated withcreatine or creatine analogs, including but not limited to thosediseases of the nervous system described in detail above. Others includebacterial or fungal infections of the nervous system. Creatine oranalogs of creatine can be used to reduce the severity of a disease,reduce symptoms of primary disease episodes, or prevent or reduce theseverity of recurrent active episodes. Creatine, creatine phosphate oranalogs such as cyclocreatine and cyclocreatine phosphate can be used totreat progressive diseases. Many creatine analogs can cross theblood-brain barrier. For example, treatment can result in the reductionof tremors in Parkinson's disease, and other linical symptoms.

Modes of Administration

[0117] The creatine compound can be administered to the afflictedindividual alone or in combination with another creatine analog or otheragent. The creatine compounds can be administered as pharmaceuticallyacceptable salts in a pharmaceutically acceptable carrier, for example.The compound may be administered to the subject by a variety of routes,including, but not necessarily limited to, oral (dietary), transdermal,or parenteral (e.g., subcutaneous, intramuscular, intravenous injection,bolus or continuous infusion) routes of administration, for example. Aneffective amount (i.e., one that is sufficient to produce the desiredeffect in an individual) of a composition comprising a creatine analogis administered to the individual. The actual amount of drug to beadministered will depend on factors such as the size and age of theindividual, in addition to the severity of symptoms, other medicalconditions and the desired aim of treatment.

[0118] Previous studies have described the administration and efficacyof creatine compounds in vivo. For example, creatine phosphate has beenadministered to patients with cardiac diseases by intravenous injection.Up to 8 grams/day were administered with no adverse side effects. Theefficacy of selected creatine kinase substrate analogs to sustain ATPlevels or delay rigor during ischemic episodes in muscle has beeninvestigated. On one study, cyclocreatine was fed to mice, rats andchicks, and appeared to be well-tolerated in these animals. Newlyhatched chicks were fed a diet containing 1% cyclocreatine. In thepresence of antibiotics, the chicks tolerated 1% cyclocreatine withoutsignificant mortality, although the chicks grew more slowly than controlchicks (Griffiths, G. R. and J. B. Walker, J. Biol. Chem. 251(7):2049-2054 (1976)). In another study, mice were fed a diet containing 1%cyclocreatine for 10 days (Annesley, T. M. and J. B. Walker, J. Biol.Chem. 253(22): 8120-8125 (1978)). Cyclocreatine has been feed to mice atup to 1% of their diet for 2 weeks or for over 4 weeks without grossadverse effects. Lillie et al., Cancer Res., 53: 3172-3178 (1993).Feeding animals cyclocreatine (e.g., 1% dietary). has been shown to leadto accumulation of cyclocreatine in different organs in mMconcentrations. For example, cyclocreatine was reported to be taken upby muscle, heart and brain in rats receiving dietary 1% cyclocreatine.Griffiths, G. R. and J. B. Walker, J. Biol. Chem. 251(7): 2049-2054(1976). As shown previously, antiviral activity of cyclocreatine isobserved on administering 1% dietary cyclocreatine. Many of theabove-referenced studies show that creatine analogs are been shown to becapable of crossing the blood-brain barrier.

[0119] The creatine compound can be formulated according to the selectedroute of administration (e.g., powder, tablet, capsule, transdermalpatch, implantable capsule, solution, emulsion). An appropriatecomposition comprising a creatine analog can be prepared in aphysiologically acceptable vehicle or carrier. For example, acomposition in tablet form can include one or more additives such as afiller (e.g., lactose), a binder (e.g., gelatin, carboxymethylcellulose,gum arabic), a flavoring agent, a coloring agent, or coating material asdesired. For solutions or emulsions in general, carriers may includeaqueous or alcoholic/aqueous solutions, emulsions or suspensions,including saline and buffered media. Parenteral vehicles can includesodium chloride, solution, Ringer's dextrose, dextrose and sodiumchloride, lactated Ringer's or fixed oils. In addition, intravenousvehicles can include fluid and nutrient replenishers, and electrolytereplenishers, such as those based on Ringer's dextrose. Preservativesand other additives can also be present. For example, antimicrobial,antioxidant, chelating agents, and inert gases can be added. (See,generally, Remington's Pharmaceutical Sciences, 16th Edition, Mack, Ed.,.1980).

[0120] The term “administration” is intended to include routes ofadministration which allow the creatine compounds to perform theirintended function(s) of preventing, ameliorating, arresting, and/oreliminating disease(s) of the nervous system in a subject. Examples ofroutes of administration which may be used include injection(subcutaneous, intravenous, parenterally, intraperitoneally, etc.),oral, inhalation, transdermal, and rectal. Depending on the route ofadministration, the creatine-like compound may be coated with or in amaterial to protect it from the natural conditions which maydetrimentally effect its ability to perform its intended function. Theadministration of the creatine-like compound is done at dosages and forperiods of time effective to reduce, ameliorate or eliminate thesymptoms of the nervous system disorder. Dosage regimes may be adjustedfor purposes of improving the therapeutic or prophylactic response ofthe compound. For example, several divided doses may be administereddaily or the dose may be proportionally reduced as indicated by theexigencies of the therapeutic situation.

[0121] In addition, the methods of the instant invention comprisecreatine compounds effective in crossing the blood-brain barrier.

[0122] The creatine compounds of this invention may be administeredalone or as a mixture of creatine compounds, or together with anadjuvant or other drug. For example, the creatine compounds may becoadministered with other different art-recognized moieties such asnucleotides, neurotransmitters, agonists or antagonists, steroids,immunomodulators, immunosuppresants, vitamins, endorphins or other drugswhich act upon the nervous system or brain.

[0123] Creatine Kinase Isoenzymes in the Brain

[0124] Cells require energy to survive and to carry out the multitude oftasks that characterize biological activity. Cellular energy demand andsupply are generally balanced and tightly regulated for economy andefficiency of energy use. Creatine kinase plays a key role in the energymetabolism of cells with intermittently high and fluctuating energyrequirements such as skeletal and cardiac muscle, brain and neuraltissues, including, for example, the retina, spermatozoa andelectrocytes. As stated above, the enzyme catalyzes the reversibletransfer of the phosphoryl group from creatine phosphate to ADP, togenerate ATP. There are multi-isoforms of creatine kinase (CK) whichinclude muscle (CK-MM), brain (CK-BB) and mitochondrial (CK-Mia, CK-Mib)isoforms.

[0125] Experimental data suggest that CK is located near the sites incells where energy generation occurs; e.g., where force generation bymotor proteins takes place, next to ion pumps and transporters inmembranes and where other ATP-dependent processes take place. It seemsto play a complex multi-faceted role in cellular energy homeostasis. Thecreatine kinase system is involved in energy buffering/energy transportactivities. It also is involved in regulating ADP and ATP levelsintracellularly as well as ADP/ATP ratios. Proton buffering andproduction of inorganic phosphate are important parts of the system.

[0126] In the brain, this creatine kinase system is quite active.Regional variations in CK activity with comparably high levels incerebellum were reported in studies using native isoenzymeelectrophoresis, or enzymatic CK activity measurements in either tissueextracts or cultured brain cells. Chandler et al. Stroke, 19: 251-255(1988), Maker et al. Exp. Neurol., 38: 295-300 (1973), Manos.et al. J.Neurol. Chem., 56: 2101-2107 (1991). In particular, the molecular layerof the cerebellar cortex contains high levels of CK activity (Maker etal. id. (1973) Kahn Histochem., 48: 29-32 (1976) consistent with therecent 3′P-NMR findings which indicate that gray matter shows a higherflux through the CK reaction and higher creatine phosphateconcentrations as compared to white matter (Cadoux-Hudson et al.FASEBJ., 3: 2660-2666 (1989), but also high levels of CK activity wereshown in cultured oligodendrocytes (Manos et al. id. (1991), Molloy etal. J. Neurochem., 59: 1925-1932 (1992), typical glial cells of thewhite matter. The brain CK isoenzyme CK-BB is the major isoform found inthe brain. Lower amounts of muscle creatine kinase (CK-MM) andmitochondrial creatine kinase (CK-Mi) are found.

[0127] Localization and Function of CK Isoenzymes in Different Cells ofthe Nervous System

[0128] Brain CK (CK-BB) is found in all layers of the cerebellar cortexas well as in deeper nuclei of the cerebellum. It is most abundant inBergmann glial cells (BGC) and astroglial cells, but is also found inbasket cells and neurons in the deeper nuclei. Hemmer et al., Eur. J.Neuroscience, 6: 538-549 (1994), Hemmer et al. Dev. Neuroscience, 15:3-5 (1993). The BGC is a specialized type of astroglial cell. Itprovides the migratory pathway for granule cell migration from theexternal to the internal granule cell layer during cerebellardevelopment. Another main function of these cells is the proposedATP-dependent spatial buffering of potassium ions released during theelectrical activity of neurons (Newman et al. Trends Neuroscience, 8:156-159 (1985), Reichenbach, Acad. Sci New York, (1991), pp. 272-286.Hence, CK-BB seems to be providing energy (ATP) for migration as well asK⁺ buffering through regulation of the Na⁺/K⁺ ATPase. The presence ofCK-BB in astrocytes (Manos et al. id. 1991, Hemmer et al. id. 1994,Hemmer et al. id. 1993) may be related to the energy requirements ofthese cells for metabolic interactions with neurons; e.g., tricarboxylicacid cycle (TCA) metabolite and neurotransmitter trafficking. Hertz, CanJ. Physiol. Pharnacol., 70: 5145-5157 (1991).

[0129] The Purkinje neurons of the cerebellum play a very important rolein brain function. They receive excitatory input from parallel fibersand climbing fibers, they represent the sole neuronal output structuresof the cerebellar cortex. Calcium mediated depolarizations in Purkinjecell dendrites are thought to play a central role in the mechanism ofcerebellar motoric learning. Ito Corr. Opin. Neurobiol., 1: 616620(1991). High levels of muscle CK (CK-MM) were found in Purkinje neurons.Hemmer et al. id. (1994), Hemmer et al., id. (1993). There is strongevidence to support that CK-MM is directly or indirectly coupled toenergetic processes needed for Ca⁺⁺ homeostasis or to cellular processestriggered by this second messenger.

[0130] The glomerular structures of the cerebellum contain high levelsof CK-BB and mitochondrial CK (CK-Mi). Large amounts of energy areneeded in these structures for restoration of potassium ion gradientspartially broken down during neuronal excitation as well as formetabolic and neurotransmitter trafficking between glial cells andneurons. Hertz et al., id. (1991). The presence of CK in thesestructures may be an indication that part of the energy consumed inthese giant complexes might be supported by the creatine kinase system.

[0131] In neurons, CK-BB is found in association with synaptic vesicles(Friedhoff and Lemer, Life Sci., 20: 867-872 (1977) as well as withplasma membranes:(Lim et al., J. Neurochem., 41: 1177-1182 (1983)).

[0132] There is evidence to suggest that CK is bound to synapticvesicles and to the plasma membrane in neurons may be involved inneurotransmitter release as well as in the maintenance of membranepotentials and the restoration of ion gradients before and afterstimulation. This is consistent with the fact that high energy turnoverand concomitantly high CK concentrations have been found in thoseregions of the brain that are rich in synaptic connections; e.g., in themolecular layer of the cerebellum, in the glomerular structures of thegranule layer and also in the hippocampus. The observation that a risein CK levels observed in a fraction of brain containing nerve endingsand synapses, parallels the neonatal increase in Na⁺/K⁺ ATPase is alsosuggestive that higher levels of creatine phosphates and CK arecharacteristic of regions in which energy expenditure for processes suchas ion pumping are large. Erecinska and Silver, J. Cerebr. Blood Flowand Metabolism, 9: 2-19 (1989). In addition, protein phosphorylationwhich plays an important role in brain function is also through toconsume a sizable fraction of the total energy available in those cells(Erecinska and Silver, id. 1989). Finally, CK, together withnerve-specific enolase belongs to a group of proteins known as slowcomponent b (SCb). These proteins are synthesized in neuronal cell bodyand are directed by axonal transport to the axonal extremities. Bradyand Lasek, Cell, 23: 515-523 (1981), Oblinger et al., J. Neurol., 7:433-462 (1987) The question of whether CK participates in the actualenergetics of axonal transport remains to be answered.

[0133] In conclusion, the CK system plays a key role in the energeticsof the adult brain. This is supported by ³¹P NMR magnetization transfermeasurements showing that the pseudo first order rate constant of the CKreaction in the direction of ATP synthesis as well as CK flux correlatewith brain activity which is measured by EEG as well as by the amount ofdeoxyglucose phosphate formed in the brain after administration ofdeoxyglucose. The present inventors have discovered that diseases of thenervous system can be treated by modulating the activity of the creatinekinase/creatine phosphate pathway.

[0134] The Role of Creatine Kinase in Treating-Diseases of the NervousSystem

[0135] The mechanisms by which nerve cell metabolites are normallydirected to specific cell tasks is poorly understood. It is thought thatnerve cells, like other cells, regulate the rate of energy production inresponse to demand. The creatine kinase system is active in many cellsof the nervous system and is thought to play a role in the allocation ofhigh energy phosphate to many diverse neurological processes, such asneurotransmitter biosynthesis, electrolyte flux and synapticcommunication. Neurological function requires significant energy andcreatine kinase appears to play an important role in controlling theflow of energy inside specialized exitable cells such as neurons. Theinduction of creatine kinase, the BB isozyme and the brain mitochondrialcreatine kinase in particular, results in the generation of a highenergy state which could sustain or multiply the pathological process indiseases of the nervous system. Creatine kinase induction also causesrelease of abnormally elevated cellular energy reserves which appear tobe associated with certain diseases of the nervous system. Conversely,suppression of the creatine kinase system, or abberances in it, induce alow energy state which could result in or assist in the death in theprocess of all the nervous system.

[0136] The components of the creatine kinase/phosphocreatine systeminclude the enzyme creatine kinase, the substrates creatine and creatinephosphate, and the transporter of creatine. Some of the functionsassociated with this system include efficient regeneration of energy incells with fluctuating and high energy demand, phosphoryl transferactivity, ion transport regulation, cytoskeletal association, nucleotidepool preservation, proton buffering, and involvement in signaltransduction pathways. The creatine kinase/phosphocreatine system hasbeen shown to be active in neurons, astrocytes, oligodendrocytes, andSchwann cells. The activity of the enzyme has been shown to beup-regulated during regeneration and down-regulated in degenerativestates, and aberrant in mitochondrial diseases.

[0137] Many diseases of the nervous system are thought to be associatedwith abnormalities in an energy state which could result in imbalancedion transport neurotransmitter release and result in cell death It hasbeen reported that defects in mitochondrial respiration enzymes andglycolytic enzymes may cause impairment of cell function.

[0138] Without wishing to be bound by theory, it is thought that if theinduction or inhibition of creatine kinase is a cause or a consequenceof disease, modulating its activity, may block the disease. Modulatingits activity would modulate energy flow and affect cell function.Alternatively, another possibility is that creatine kinase activitygenerates a product which affects neurological function. For example,creatine phosphate may donate a phosphate to a protein to modify itsfunction (e.g., activity, location). If phosphocreatine is such aphosphate donor, creatine analogs which are phosphorylatable orphosphocreatine analogs may competitively inhibit the interaction ofphosphocreatine with a target protein thereby directly or indirectlyinterfering with nervous system functions. Alternatively,phosphorylatable creatine analogs with altered phosphoryl group transferpotential may tie up phosphate stores preventing efficient transfer ofphosphate to targets. A neurological disease could be associated withdown regulation of creatine kinase activity. In such cases,replenishment of the substrates, e.g., creatine, creatine phosphate or asubstrate analog, which could sustain ATP production for an extended oftime, with other activators of the enzyme could be beneficial fortreatment of the disease.

[0139] Ingestion of creatine analogs has been shown to result inreplacement of tissue phosphocreatine pools by synthetic phosphagenswith different kinetic and thermodynamic properties. This results insubtle changes of intracellular energy metabolism, including theincrease of total reserves of high energy phosphate (see refs. Roberts,J. J. and J. B. Walker, Arch Biochem. Biophys 220(2): 563-571 (1983)).The replacement of phosphocreatine pools with slower acting syntheticphosphagens, such as creatine analogs might benefit neurologicaldisorders by providing a longer lasting source of energy. One suchanalog, cyclocreatine (1-carboxymethyl-2-aminoimidazolidine) modifiesthe flow of energy of cells in stress and may interfere with ATPutilization at sites of cellular work.

[0140] The pathogenesis of nerve cell death in neurodegenerativediseases is unknown. A significant amount of data has supported thehypothesis that an impairment of energy metabolism may underlie the slowexitotoxic neuronal death. Several studies have demonstratedmitochondrial or oxidative defects in neurodegenerative diseases.Impaired energy metabolism results in decreases in high energy phosphatestores and a deteriorating membrane potential. Under these conditionsthe voltage sensitive Mg2+block of NMDA receptors is relieved, allowingthe receptors to be persistently activated by endogenbus concentrationsof glutamate. In this way, energy related metabolic defects may lead toneuronal death by a slow exitotoxic mechanism. Recent studies indicatethat such a mechanism occurs in vivo, and it may play a role in animalmodels of Huntington's disease and Parkinson's disease.

[0141] As discussed in detail above, the creatine kinase/creatinephosphate energy system is only one component of an elaborate energy-generating system found in the nervous system. The reaction catalyzed bythis system results in the rapid regeneration of energy in the form ofATP at sites of cellular work. In the mitochondria the enzyme is linkedto the oxidative phosphorylation pathway that has been implicated indiseases of the nervous system. There the enzyme works in the reversedirection where it stores energy in the form of creatine phosphate.

[0142] The invention is further illustrated in the following examples,which prove that creatine compounds, represented by creatine itself andthe analogue cyclocreatine, are neuroprotective agents in animal modelsused for neurodegenerative diseases, specifically, Huntington's diseaseand Parkinson's disease.

EXAMPLES Example 1: Malonate as a model of Huntington's Disease

[0143] A series of reversible and irreversible inhibitors of enzymesinvolved in energy generating pathways have been used to generate animalmodels for neurodegenerative diseases such as Parkinson's andHuntington's diseases.

[0144] Inhibitors of the enzyme succinate dehydrogenase which impactcellular energy state have been used successfully to generate a modelfor Huntington's disease. Brouillet et. al., J.Neurochem. 60: 356-359(1993); Beal et. al., J. Neurosci. 13: 4181-4192 (1993); Henshaw et.al., Brain Research 647: 161-166 (1994); Beal et al., J.Neurochem. 61:1147-1150 (1993). The enzyme succinate dehydrogenase plays a centralrole in both the tricarboxilic acid cycle as well as the electrontransport chain in the mitochindria. It's reversible inhibitor malonatehas recently been evaluated in animals. Intrastriatal injections ofmalonate in rats was shown to produce dose dependent striatalexcitotoxic lesions which are attenuated by both competitive and noncompetitive NMDA antagonist. Henshaw et. al., Brain Research 647:161-166 (1994). Furthermore the glutamate release inhibitor lamotriginealso attenuates the lesions. Co-injection with succinate blocks thelesions, consistent with an effect on succinate dehydrogenase. Thelesions are accompanied by a significant reduction in ATP levels as wellas significant increase in lactate levels in vivo as shown by chemicalshift resonance imaging. Beal et al., J.Neurochem. 61: 1147-1150 (1993).Further more the increases in lactate are greater in older animalsconsistent with a marked age- of the lesions. Histological studies haveshown that the lesion spares NADPH- diaphorase neurons. Somatostatinconcentrations were also spared. In vivo magnetic resonance imaging oflesions shows a significant correlation between increasing lesion sizeand lactate production.

[0145] A series of experiments demonstrated that the administration ofcoenzyme Q₁₀ or nicotinamide produced dose dependent protection againstthe lesions in the malonate animal model. These compounds attenuated ATPdepletions produced by malonate in vivo. Further more theco-administration of coenzyme Q₁₀ with nicotinamide attenuated thelesions and reduced increases in lactate which occurred afterintrastriatal malonate injections.

[0146] All of the above mentioned studies supported malonate as a usefulmodel for the neuropathologic and neurochemical features of Huntington'sdisease. These lesions produced the same pattern of cellular sparingwhich is seen in Huntington's disease. There is a depletion of striatalspiny neurons yet a relative preservation of the NADPH diaphoraseinterneurons. Furthermore there is an increase in lactate concentrationswhich has been observed in Huntington's disease.

[0147] The effect of creatine and it's analogue cyclocreatine wereevaluated as representatives of creatine compounds in this malonatemodel for Huntington's disease. Both compounds were administered orallyas 1% of the diet. This mode of administration was based on previousstudies were significant build up of compounds in organs high increatine kinase activity such as the muscle and the brain wasdemonstrated and were 1% cyclocreatine in the diet was shown to inhibittumor growth and viral replication. Lillie et al Cancer Research, 53:3172-3178 (1993); Lillie et. al., Antiviral Research 23: 203-218 (1994).

[0148] Male Sprague-Dawley rats (Charles River, Wilmington, Mass.)weighing around 300 gms were used in this experiment. Animals weredivided into three groups, 7 used as controls, 8 treated with creatineand 8 treated with cyclocreatine. Group one was fed regular chow,whereas the other groups were given chow enriched with 1% creatine orcyclocreatine. The compounds were administered for two weeks prior tothe administration of malonate and then for a further week prior tosacrifice. Malonate was dissolved in distilled deionized water and thepH was adjusted to 7.4 with 0.1 M HCl. Intrastriatal injections of 1.5μl of malonate containing 3 μmol were made into the left striatum at thelevel of the Bregma 2.4 mm lateral to the midline and 4.5 mm ventral tothe dura. Animals were sacrificed at 7 days by decapitation and thebrains were quickly removed and placed in ice cold 0.9% saline solution.Brains were sectioned at 2 mm intervals in a brain mold. Slices werethen placed posterior side down in 2% 2,3,5-tiphenyltetrazoliumchloride. Slices were stained in the dark at room temperature for 30minutes and then removed and placed in 4% paraformaldehyde pH 7.3.Lesions, noted by pale staining, were evaluated on the posterior surfaceof each section using a Bioquant 4 system by an experienced histologistblinded by experimental conditions. These measurements have beenvalidated by comparing them to measurements obtained on adjacent Nisslstain sections to demonstrate the validity of the method. The data areexpressed as the means +/− standard error of means (SEM). Statisticalcomparisons were made by unpaired Student's t test or one-way analysisof variance with the Fisher protected least significant difference(PLSD) test.

[0149] As shown in FIG. 1, the treatment of animals with creatineproduced a significant neuroprotective effect against the intrastriatalinjection of malonate. Cyclocreatine also produced some neuroprotectiveeffect. These results implicate the enzyme creatine kinase in pathwaysinvolved in neuronal cell death and supports the therapeutic benefit ofthe creatine compounds in the treatment of neurodegenerative diseasesand mitochondrial encephalopathies. Substantial evidence exists for animpairment of mitochondrial energy metabolism in a number ofneurodegenerative diseases. This is particularly true in the case ofHuntington's disease. The present lesions model Huntington's diseasequite well, thus, the results indicate that creatine compounds areuseful in slowing the degenerative process in this illness. Otherneurodegenerative diseases which were shown to have underlying defectsin energy generation also are expected to be slowed by creatinecompounds.

Example 2: MPTP as a Model for Parkinson's Disease

[0150] MPTP, or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine is aneurotoxin which produces a Parkinsonian syndrom in both man andexperimental animals. The initial report was by a chemist who wassynthesizing and self injecting an opiate analogue. He inadvertentlysynthesized MPTP and developed profound Parkinsonism. Subsequentpathologic studies showed severe degeneration in the pars compacta ofthe substantia nigra. A large outbreak subsequently occured inCalifornia. These patients developed typical symptoms of Parkinsonism.They also had positron emission tomography done which showed a markedloss of dopaminergic innervation of the stiatum.

[0151] Studies of the mechanism of MPTP neurotoxicity show that itinvolves the generation of a major metabolite, MPP⁺. This metabolite isformed by the activity of monoamine oxidase on MPTP. Inhibitors ofmonoamine oxidase block the neurotoxicity of MPTP in both mice andprimates. The specificity of the neurotoxic effects of MPP⁺ fordoparinergic neurons appears to be due to the uptake of MPP⁺ by thesynaptic dopamine transporter. Blockers of this transporter prevent MPP⁺neurotoxicity. MPP⁺ has been shown to be a relatively specific inhibitorof mitochondrial complex I. activity. It binds to complex I at theretenone binding site. In vitro studies show that it produces animpairment of oxidative phosphorylation. In vivo studies have shown thatMPTP can deplete striatal ATP concentrations in mice. It has beendemonstrated that MPP+ administered intrastriatally in rats producessignificant depletion of ATP as well as increases in lactate confined tothe striatum at the site of the injections. The present inventors haverecently demonstrated that coenzyme Q₁₀ which enhances ATP productioncan significantly protect against MPTP toxicity in mice.

[0152] The effect of two representative creatine compounds, creatine andcyclocreatine, were evaluated using this model. Creatine andcyclocreatine were administered as 1% formulation in the feed of animalsand was administered for three weeks before MPTP treatment. MPTP wasadministered i.p. at a dose of 15 mg/kg every 2hours for fiveinjections. The animals then remained on either creatine or cyclocreainesupplemented diets for 1 week before sacrifice. The mice examined weremale Swiss Webster mice weighing 30-35 grams obtained from TaconicFarms. Control groups recieved either normal saline or MPTPhydrochloride alone. MPTP was administered in 0.1 ml of water. The MPTPwas obtained from Research Biochemicals. Eight to twelve animals wereexamined in each group. Following sacrifice the two striatal wererapidly dissected and placed in chilled 0.1 M perchloric acid. Tissuewas subsequently sonicated, and aliquots were taken for proteinquantification using a fluorometer assay. Dopamine,3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) werequantified by HPLC with 16 electrode electrochemical detection.Concentrations of dopamine and metabolites were expressed as nmol/mgprotein. The statistical significance of differences was determined byone-way ANOVA followed by Fisher PLSDpost-hoc test to compare groupmeans.

[0153] The results are shown in FIG. 2. Oral administration of eithercyclocreatine or creatine significantly protected against DOPACdepletions induced by MPTP. Cyclocreatine was effective against MPTPinduced depletions of homovanillic acid. Both administration of creatineand cyclocreatine produce significant neuroprotection against MPTPinduced dopamine depletions. The neuroprotective effect produced bycyclocreatine was greater than that seen with creatine alone.

[0154] These results indicate that the administration of creatine orcyclocreatine can produce significant neuroprotective effects againstMPTP induced dopaminiergic toxicity. These results imply that thesecompounds are useful for the treatment of Parkinson's disease. The datafurther establishes the importance of the creatine kinase system inbuffering energy and survival of neuronal tissue. Therefor creatinecompounds which can sustain energy production in neurons are going toemerge as a new class of protective agents of benefit therapeutically inthe treatment of neurodegenerative diseases where impairment of energyhas been established.

[0155] Equivalents

[0156] Those skilled in the art will recognize, or be able to ascertainusing no more than routine experimentation; many equivalents to thespecific embodiments of the invention described herein. Such equivalentsare intended to be encompassed by the following claims.

What is claimed is:
 1. A method for treating a subject afflicted with anervous system disease comprising administering to the subject an amountof creatine, creatine phosphate or a creatine analog or a salt thereofcompound sufficient to prevent, reduce, ameliorate or eliminate saiddisease.
 2. The method of claim 1 wherein the subject is a mammal. 3.The method of claim 1 wherein the subject is human.
 4. A method fortreating a subject for diseases of the nervous system comprising:administering an effective amount of a creatine compound to a subjectsuch that the subject is treated for diseases of the nervous system,wherein the creatine compound is of the general formula:

and pharmaceutically acceptable salts thereof, wherein: a) Y is selectedfrom the group consisting of: —CO₂H, —NHOH, —NO₂, —SO₃H, —C(═O)NHSO₂Jand —P(═O)(OH)(OJ), wherein J is selected from the group consisting of:hydrogen, C₁-C₆ straight chain alkyl, C₃-C₆ branched alkyl, C₂-C₆alkenyl, C₃-C₆ branched alkenyl, and aryl; b) A is selected from thegroup consisting of C, CH, C₁-C₅alkyl, C₂-C₅alkenyl, C₂-C₅alkynyl, andC₁-C₅ alkoyl chain, each having 0-2 substituents which are selectedindependently from the group consisting of 1) K, where K is selectedfrom the group consisting of C₁-C₆ straight alkyl, C₂-C₆ straightalkenyl, C₁-C₆ straight alkoyl, C₃-C₆ branched alkyl, C₃-C₆ branchedalkenyl, and C₄-C₆ branched alkoyl, K having 0-2 substituentsindependently selected from the group consisting of bromo, chloro, epoxyand acetoxy; 2) an aryl group selected from the group consisting of a1-2 ring carbocycle and a 1-2 ring heterocycle, wherein the aryl groupcontains 0-2 substituents independently selected from the groupconsisting of: —CH₂L and —COCH₂L where L is independently selected fromthe group consisting of: bromo, chloro, epoxy and acetoxy; and 3) —NH—M,wherein M is selected from the group consisting of hydrogen, C₁-C₄alkyl, C₂-C₄ alkenyl, C₁-C₄ alkoyl, C₃-C₄ branched alkyl, C₃-C₄ branchedalkenyl, and C₄ branched alkoyl; c) X is selected from the groupconsisting of NR₁, CHR₁, CR₁, O and S, wherein R₁ is selected from thegroup consisting of: 1) hydrogen; 2) K where K is selected from thegroup consisting of: C₁-C₆ straight alkyl, C₂-C₆ straight alkenyl, C₁-C₆straight alkoyl, C₃-C₆ branched alkyl, C₃-C₆ branched alkenyl, and C₄-C₆branched alkoyl, K having 0-2 substituents independently selected fromthe group consisting of bromo, chloro, epoxy and acetoxy; 3) an arylgroup selected from the group consisting of a 1-2 ring carbocycle and a1-2 ring heterocycle, wherein the aryl group contains 0-2 substituentsindependently selected from the group consisting of —CH₂L and —COCH₂Lwhere L is independently selected from the group consisting of bromo,chloro, epoxy and acetoxy; 4) a C₅-C₉a-amino-w-methyl-w-adenosylcarboxylic acid attached via the w-methylcarbon; 5) a C₅-C₉ a-amino-w-aza-w-methyl-w-adenosylcarboxylic acidattached via the w-methyl carbon; and 6) a C₅-C₉a-amino-w-thia-w-methyl-w-adenosylcarboxylic acid attached via thew-methyl carbon; d) Z₁ and Z₂ are chosen independently from the groupconsisting of: ═O, —NHR₂, —CH₂R₂, —NR₂OH; wherein Z₁ and Z₂ may not bothbe ═O and wherein R₂ is selected from the group consisting of: 1)hydrogen; 2) K, where K is selected from the group consisting of C₁-C₆straight alkyl; C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆branched alkyl, C₃-C₆ branched alkenyl, and C₄-C₆ branched alkoyl, Khaving 0-2 substituents independently selected from the group consistingof: bromo, chloro, epoxy and acetoxy; 3) an aryl group selected from thegroup consisting of a 1-2 ring carbocycle and a 1-2 ring heterocycle,wherein the aryl group contains 0-2 substituents independently selectedfrom the group consisting of: —CH₂L and —COCH₂L where L is independentlyselected from the group consisting of: bromo, chloro, epoxy and acetoxy;4) a C₄-C₈ a-amino-carboxylic acid attached via the w-carbon; 5) B,wherein B is selected from the group consisting of: —CO₂H, —NHOH, —SO₃H,—NO₂, OP(═O)(OH)(OJ) and —P(═O)(OH)(OJ), wherein J is selected from thegroup consisting of: hydrogen, C₁-C₆ straight alkyl, C₃-C₆ branchedalkyl, C₂-C₆ alkenyl, C₃-C₆ branched alkenyl, and aryl, wherein B isoptionally connected to the nitrogen via a linker selected from thegroup consisting of: C₁-C₂ alkyl, C₂ alkenyl, and C₁-C₂ alkoyl; 6) —D—E,wherein D is selected from the group consisting of: C₁-C₃ straightalkyl, C₃ branched alkyl, C₂-C₃ straight alkenyl, C₃ branched alkenyl,C₁-C₃ straight alkoyl, aryl and aroyl; and E is selected from the groupconsisting of: —(PO₃)_(n)NMP, where n is 0-2 and NMP is ribonucleotidemonophosphate connected via the 5′-phosphate, 3′-phosphate or thearomatic ring of the base, —[P(═O)(OCH₃)(O)]_(m)—Q, where m is 0-3 and Qis a ribonucleoside connected via the ribose or the aromatic ring of thebase; —[P(═O)(OH)(CH₂)]_(m)—Q, where m is 0-3 and Q is a ribonucleosideconnected via the ribose or the aromatic ring of the base; and an arylgroup containing 0-3 substituents chosen independently from the groupconsisting of: Cl, Br, epoxy, acetoxy, —OG, —C(═O)G, and —CO₂G, where Gis independently selected from the group consisting of: C₁-C₆ straightalkyl, C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆ branchedalkyl, C₃-C₆ branched alkenyl, C₄-C₆ branched alkoyl, wherein E may beattached to any point to D, and if D is alkyl or alkenyl, D may beconnected at either or both ends by an amide linkage; and 7) —E, whereinE is selected from the group consisting of —(PO₃)_(n)NMP, where n is 0-2and NMP is a ribonucleotide monophosphate connected via the5′-phosphate, 3′-phosphate or the aromatic ring of the base;—[P(═O)(OCH₃)(O)]_(m)—Q, where m is 0-3 and Q is a ribonucleosideconnected via the ribose or the aromatic ring of the base;—[P(═O)(OH)(CH₂)]_(m)—Q, where m is 0-3 and Q is a ribonucleosideconnected via the ribose or the aromatic ring of the base; and an arylgroup containing 0-3 substituents chose independently from the groupconsisting of: Cl, Br, epoxy, acetoxy, —OG, —C(═O)G, and —CO₂G, where Gis independently selected from the group consisting of: C₁-C₆ straightalkyl, C₂-C₆ straight alkenyl, C₁-C₆ straight alkoyl, C₃-C₆ branchedalkyl, C₃-C₆ branched alkenyl, C₄-C₆ branched alkoyl; and if E is aryl,E may be connected by an amide linkage; e) if R₁ and at least one R₂group are present, R₁ may be connected by a single or double bond to anR₂ group to form a cycle of 5 to 7 members; f) if two R₂ groups arepresent, they may be connected by a single or a double bond to form acycle of 4 to 7 members; and g) if R₁ is present and Z₁ or Z₂ isselected from the group consisting of —NHR₂, —CH₂R₂ and —NR₂OH, then R₁may be connected by a single or double bond to the carbon or nitrogen ofeither Z₁ or Z₂ to form a cycle of 4 to 7 members.
 5. The method ofclaim 4 wherein the treatment comprises reducing or eliminating symptomsassociated with a preexisting disease of the nervous system.
 6. Themethod of claim 4 wherein the treatment comprises preventing theoccurrence of diseases of the nervous system within the subject.
 7. Themethod of claim 4 wherein the creatine compound is creatine.
 8. Themethod of claim 4 wherein the creatine compound is creatine phosphate.9. The method of claim 4 wherein the creatine compound is cyclocreatine.10. The method of claim 4 wherein the creatine compound is cyclocreatinephosphate.
 11. The method of claim 4 wherein the creatine compound ishomocyclocreatine.
 12. The method of claim 4 wherein the disease of thenervous system is selected from the groups consisting of neuropathies;Alzheimer disease, Parkinson's disease, Huntington's disease, motorneuron disease, traumatic nerve injury, multiple sclerosis, acutedisseminated encephalomyelitis, acute necrotizing hemorrhagicleukoencephalitis, dysmyelination disease, mitochondrial disease,migrainous disorder, bacterial infection, fungal infection, stroke,aging, dementia, peripheral nervous system diseases and mental disorderssuch as depression and schizophrenia.
 13. The method of claim 12 whereinthe creatine compound is selected from the group consisting of creatine,creatine phosphate, cyclocreatine and cyclocreatine phosphate.
 14. Themethod of claim 4 further comprising coadministering to the subject aneurotransmitter, a neurotransmitter analog, a steroid, animmunomodulating agent, or an immune suppressive agent.
 15. The methodof claim 4 wherein the subject is treated for diseases of the nervoussystem by reducing or eliminating symptoms associated with a preexistingdiseases of the nervous system.
 16. The method of claim 4 wherein thesubject is treated for diseases of the nervous system by preventing theoccurrence of a disease of the nervous system within the subject.
 17. Amethod for alleviating in a subject being treated for a nervous systemdisease toxic side effects of drugs used to treat the nervous systemdiseases, comprising administering to the subject an amount of acreatine, creatine phosphate or a creatine analog, or a salt thereof,sufficient to prevent, reduce, ameliorate or alleviate said toxic sideeffects.
 18. The method of claim 17 wherein the creatine analog iscyclocreatine or cyclocreatine phosphate.